Aircraft wings typically include front and rear spars, ribs extending between the spars, and upper and lower covers (skins) extending between the spars. The outer surfaces of the covers form part of the aerodynamic wing profile. The spars, ribs and covers are assembled to form a wing box structure.
An existing method for forming rib-spar joints between the ribs and the spars during assembly of the wing includes manually installing the ribs and adjusting their position based on gap measurements taken with feeler gauges to the adjacent spar structure using tooling gauges placed at the four corners of each rib component. This method has several drawbacks. As it was a manual process, it was subject to operator error. The assembly process was time consuming often requiring several checking and adjusting cycles to achieve the optimum position. Each rib required a set of eight unique gauges, resulting in a large amount of tooling.
In addition, with the move from traditional metallic to composite materials, e.g. carbon fibre reinforced plastic (CFRP), for at least some of the wing box structural components, the tolerances have increased adding more complexity and variation to the assembly process.
Furthermore, whereas aircraft wings have traditionally been assembled in a vertical orientation (i.e. ribs upright), there are advantages in assembling the wing in a horizontal orientation (i.e. level flight orientation). However, manual manipulation of the structural wing components during assembly is made more difficult with this horizontal orientation due to the influence of gravity.